Communication systems in which a common channel or frequency is shared among multiple transmitters are degraded by collisions in which a receiver is concurrently presented with two or more messages from two or more different transmitters. Data collisions present a contention problem that is prevalent in systems in which there is little or no channel arbitration, and can even occur in arbitrated systems or systems utilizing a network control protocol. In an example involving automatic (utility) meter reading (AMR) systems, a central data gathering transceiver receives utility consumption and related information transmitted by a plurality of utility meter endpoints that originate the utility consumption and related information and transmit it to a data gathering transceiver. Typically, the remote transceivers transmit without concern for existing traffic in the communication channel. For example, each remote transceiver can operate in an ALOHA-type mode of operation in which it transmits data without regard to whether other transmitters may be broadcasting.
A capture effect problem is typically experienced in a shared medium system when a weak RF signal is preempted by a stronger RF signal resulting in the receiver tracking the stronger signal. This capture effect can result in loss of the original data packet as the weaker signal is overridden by the later arriving but stronger second signal. Information transmitted by the second signal is typically also lost in this scenario because the weaker first message had not been properly terminated.
The loss of data as a result of such collisions substantially reduces the information transfer performance in the communication channel. As the number of transmitters (and transmissions per unit time) increase, so too does the incidence of collisions. The overall effect inhibits the number and duration of transmissions that can be accommodated by the communication channel. In addition, collision management typically requires re-transmission of data, which further clutters the communication channel and consumes additional energy in the transmitters. If the installed transmitters are battery-powered, their useful life is reduced.